140 ALFALFA FARMING IN AMERICA. 
All the region east of the Mississippi River will 
be helped by use of ground limestone, with the ex- 
ception of some favored spots where glaciers have 
already ground the rocks to powder and mixed it 
through the land. Anywhere that alfalfa fails to 
thrive after the land has been made dry and fairly 
rich one may know that carbonate of lime is de- 
ficient. Especially may one be sure that all soils 
along the Atlantic seaboard are deficient in car- 
bonate of lime, and by supplying this lack their 
capacity for crop production may be immensely 
increased. 
The Chemistry of Lime—In ‘‘The Breeder’s Ga- 
zette’’ of July 14, 1909, Dr. Cyril G. Hopkins, agron- 
omist of the College of Agriculture, University of 
Tllinois, sets forth clearly the chemistry of lime in 
its relation to soil improvement. I quote his state- 
ment complete: 
The use of lime for soil improvement is a subject which is dis- 
cussed with a great deal of misconception and confusion, due in 
large part to the erroneous practice of referring to lime as though 
it were a chemical element. 
Lime is not an element and consequently is not an element of 
plant food. It is an alkaline substance and is known in three 
forms: the carbonate, the oxide and the hydroxide. The carbonate 
is the natural form found in rocks and soils and it consists of 
either calcium carbonate, magnesium carbonate or a double com- 
pound of calcium magnesium carbonate known as magnesian 
limestone or dolomite. When highly heated these carbonates lose 
their carbon dioxide as a volatile gas and the oxide or quicklime 
remains. This substance takes up water either from direct appli- 
eation or from the moisture of the atmosphere and changes into 
the form of hydroxide or water-slaked lime. On long exposure 
to the air the hydroxide will absorb carbon dioxide from the air 
and give off water, thus reforming the carbonate compound. Thus 
we may say that calcium carbonate (CaCO,), calcium oxide (CaO) 
